Abstract [en]

WesDyne TRC is wholly owned subsidiary company of the nuclear technology company Westinghouse Nuclear and primarily works with non destructive testing (NDT) and visual inspections of reactor tanks. Within the nuclear industry there exists a strong interest in making accurate geometrical measurements inside a reactor tank. In this work a feasibility study was done where suitable technologies were examined to find the most appropriate for this purpose. The technique that was considered most likely to be successful was active triangulation with laser. After further elaboration in the area of interest a prototype was developed and constructed along with programming, which then was tested and verified. These tests were executed in both a lab environment as in an environment appropriate to the intended application, which in this case involves measurement under water in absence of light.

Measurements of items such as EDM pits, welds and the like were utilized to evaluate the technology. In measurements performed under water the technology performs a high resolution, down to a few tens of microns, and a deviation of about 4-6 % from the nominal dimension in depth. The deviation in the plane was much lower at around 1 %. Measurement procedures are considered to have great potential and repeatable tests suggest that repeatability down to the level of resolution is achievable. In the performed tests a resolution of approximately 5, 38 and 10 microns in the three directions x, y and z are obtained, where z is depth. Potential for further improvement in the y direction exists. In these tests the limitation has been the focusing distance of the laser beam which prevents a closer scanning distance. With the prototype measurement and detection of very small deviations in the surface of measured object was possible. This has been such punch labels, dents, small cracks, circular milling patterns and scratches so small that they cannot be perceived by touch. When a flat, smooth, dull surface was measured the noise was less than 50 microns.

The discrepancy in depth can be compared with a non-linear expansion that seems change in to a slight compression when the distance to the object in the picture increases. In this thesis the reasons for the expansion/compression has not been determined.

Better and more accurate calibration methods, and proposed changes to the design, is most likely to improve the accuracy in the sense that it is less than 1 % in all directions.

Place, publisher, year, edition, pages

2011. , p. 63

Series

MMK2011:3 MKN036

Keyword [en]

Equipment for precision measurements in 3D for underwater applications